Pion-Nukleon-Wechselwirkung und die Struktur von Nukleon-Resonanzen

Schütz, C.

Book/Report

FZJ-2019-00799

Pion-Nukleon-Wechselwirkung und die Struktur von Nukleon-Resonanzen

Schütz, C. (Corresponding author)FZJ*

1995
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Berichte des Forschungszentrums Jülich 3130, 138 p. (1995)

Please use a persistent id in citations: http://hdl.handle.net/2128/21402

Report No.: Juel-3130

Abstract: We develop a meson-exchange model for pion-nucleon inter action. The starting point of our investigation is given by a dynamical model for correlated two-pionexchange in the $\pi$ N interaction. Supplemented by pole and exchange diagrams involving the nucleon and the $\Delta$ isobar this model yields a good description of elastic $\pi$ N scattering data. Implications resulting from alternative models for correlated two-pion exchange in the $\rho$ channel are discussed. By splitting up different contributions of our interaction model to P$_{33}$-wave $\pi$ N scattering the importance of the non-pole part of the interaction for the quantitative understanding of the width of the $\Delta$ isobar is demonstrated. Furthermore, we determine the $\pi$ N N and $\pi$ N $\Delta$ form factors. The second part of this work deals with the extension of our $\pi$ N interaction model to higher energies by taking into ac count coupling to inelastic reaction channels.The common goal of these calculations is to improve our understanding of the experimentally observed spectrum of the nucleon excited states. We investigate thequestion whether there is unambiguous evidence that these resonances contain a genuine three-quark 'excited state' contribution or whether they can be understood purely in terms of the underlying meson-baryon dynamics. We investigate the effect of coupling to the reaction channel $\eta$N for the understandingof the resonance N$^{*}_{S11}$ (1535) the position of which almost coincides with the $\eta$N threshold. By taking into account also coupling to the reaction channels $\pi \Delta$ and ($\sigma$ N the energy range of our model is extended into the inelastic range (up to E$_{c.m.}$ $\simeq$ 1.6 GeV) for all partial waves of $\pi$ N scattering. Within this coupled channel model we obtain a dynamical description of the Roper resonance (N$^{*}_{P11}$ (1440))without any contribution from a genuine N* resonance.

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